Abstract
Background: inadequacy of oxygenation during conventional ECMO with veno-left atrial bypass (VAB) and veno-venous bypass (VVB) can induce secondary cardiac dysfunction due to the hypoxemia of coronary blood flow. A new method of ECMO with veno-left atrial bypass (VLAB) has been devised for cases of profound respiratory failure. This method provides better oxygenation in the aortic root. In the current study, an experimental respiratory failure model was used to compare the effect of VLAB and veno-pulmonary artery bypass (VPAB) with VAB on cardiac function. Materials and Methods: Eighteen pigs (22-28kg) were anesth etized with intramuscular ketamine (50mg/kg) and intravenous sodium pentobarbital (50mg/kg). Their respiration was controlled with a volume respirator and an endotracheal tube. After thoracotomy, the control cardiac output (CO) was measured in ventilation with 100% oxygen. Then, a hypoxemic condition was induced through ventilation using a mixture of 90% nitrogen and 10% oxygen. In experiment I (n= 9), VAB and VLAB support were performed with either femoral artery perfusion or LA perfusion. In experiment II (n=9), VAB and VPAB support were each performed with femoral artery perfusion and PA perfusion. The CO was measured using an electric magnetic flowmeter. The bypass flow rate was maintained at 30% of the CO in both experiments. ECG, systemic blood pressure (BP), and central venous pressure (CVP) were continuously monitored. The cardiac contractile function (%SS) was assessed using sonomicrometry. Blood was sampled from the aortic root to measure the oxygenation (PaO2) of coronary arterial blood. Results: Pa02 levels in the aortic root were significantly higher during VLAB and VPAB than during VAB (VLAB vs. VAB: 91.2 ± 32.8mmHg vs. 48.6± 26.6mmHg, p=0.002; VPAB vs. VAB: 102± 61.7mmHg vs. 41.9 ± 14.4mmHg, p < 0.001). %SS values during VLAB and VPAB were significantly higher than during VAB (VLAB vs. VAB: 8.94 ± 2.67% vs. 7.22 ± 1.92%, p =0.030; VPAB vs. VAB: 11.0 ± 4.23% vs. 8.32 ± 3.58%, p =0.045). Conclusions: The oxygenation in the aortic root during both VLAB and VPAB is superior to that during VAB. The reduction rate of cardiac contractile function during VLAB and VPAB can also be improved relative to that during VAB under the condition of a 30% bypass assist. No difference between VLAB and VPAB was observed in respect to the oxygenation and the left ventricular function.
